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Eliza Weisman
4bfa4ffcdf
This branch changes `dispatcher::get_default` to unset the thread's current dispatcher while the reference to it is held by the closure. This prevents infinite loops if the subscriber calls code paths which emit events or construct spans. Note that this also means that nested calls to `get_default` inside of a `get_default` closure will receive a `None` dispatcher rather than the "actual" dispatcher. However, it was necessary to unset the default in `get_default` rather than in dispatch methods such as `Dispatch::enter`, as when those functions are called, the current state has already been borrowed. Before: ``` test enter_span ... bench: 3 ns/iter (+/- 0) test span_no_fields ... bench: 51 ns/iter (+/- 12) test span_repeatedly ... bench: 5,073 ns/iter (+/- 1,528) test span_with_fields ... bench: 56 ns/iter (+/- 49) test span_with_fields_record ... bench: 363 ns/iter (+/- 61) ``` After: ``` test enter_span ... bench: 3 ns/iter (+/- 0) test span_no_fields ... bench: 35 ns/iter (+/- 12) test span_repeatedly ... bench: 4,165 ns/iter (+/- 298) test span_with_fields ... bench: 48 ns/iter (+/- 12) test span_with_fields_record ... bench: 363 ns/iter (+/- 91) ``` Closes #1032 Signed-off-by: Eliza Weisman <[email protected]>